Influence analysis of complex crack geometric parameters on mechanical properties of soft rock

Soft rocks, such as coal, are afected by sedimentary efects, and the surrounding rock mass of underground coal mines is generally soft and rich in joints and cracks. A clear and deep understanding of the relationship between crack geometric parameters and rock mechanics properties in cracked rock is greatly important to the design of engineering rock mass struc‑tures. In this study, computed tomography (CT) scanning was used to extract the internal crack network of coal specimens. Based on the crack size and dominant crack number, the parameters of crack area, volume, length, width, and angle were statistically analyzed by diferent sampling thresholds. In addition, the Pearson correlation coefcients between the crack parameters and uniaxial compression rock mechanics properties (uniaxial compressive strength UCS, elasticity modulus E) were calculated to quantitatively analyze the impact of each parameter. Furthermore, a method based on Pearson coefcients was used to grade the correlation between crack geometric parameters and rock mechanical properties to determine threshold values. The results indicated that the UCS and E of the specimens changed with the varied internal crack structures of the specimens, the crack parameters of area, volume, length and width all showed negative correlations with UCS and E, and the dominant crack played an important role both in weakening strength and stifness. The crack parameters of the angle are all positively correlated with the UCS and E. More crack statistics can signifcantly improve the correlation between the parameters of the crack angle and the rock mechanics properties, and the statistics of the geometric parameters of at least 16 cracks or the area larger than 5 mm2 are suggested for the analysis of complex cracked rock masses or physical reproduction using 3D printing. The results are validated and further analyzed with triaxial tests. The fndings of this study have important reference value for future research regarding the accurate and efcient selection of a few cracks with a signifcant infuence on the rock mechanical properties of surrounding rock mass structures in coal engineering.

Influence of geometric parameters on stress concentration factors of undermatched butt joint with single V-groove under three-point bending load

In order to improve the bending load-carrying capacity （BLCC） of undermatched butt joint under three-point bending load, the influence of joint geometric parameters on stress concentration factors （SCF） at the weld bottom center and the weld toe of uudermatched butt joint with single V-groove are studied respectively based on the finite element method in this paper. Results show that the reinforcement height and the cover pass width play decisive role in the BLCC for undermatched butt joint. BLCC of undermatched butt joint can be improved by choosing the appropriate joint geometric parameters.

Optimization of Maturation of Radio-Cephalic Arteriovenous Fistula Using a Model Relating Energy Loss Rate and Vascular Geometric Parameters

The main reason for the early failure of radio-cephalic arteriovenous fistula (RCAVF) is non-maturity, which means that the blood flow rate in the fistula cannot increase to the expected value for dialysis. From a mechanical perspective, the vascular resistance at the artificially designed anastomosis causes an energy loss that affects blood flow rate growth and leads to early failure. This research studied how to maximize the RCAVF maturity and primary patency by controlling the energy loss rate. We theoretically analyzed and derived a model that evaluates the energy loss rate Eavf in RCAVF as a function of its blood vessel geometric parameters (GPs) for given flow rates. There was an aggregate of five controllable GPs in RCAVF: radial artery diameter (Dra), cephalic vein diameter (Dcv), blood vessel distance between artery and vein (h), anastomotic diameter (Da), and anastomotic angle (θ). Through this analysis, it was found that Eavf was inversely proportional to Dra, Dcv, Da, and θ, whereas proportional to h. Therefore, we recommended surgeons choose the vessels with large diameters, close distance, and increase the diameter and angle of the anastomosis to decrease the early failure of RCAVF. Simultaneously, we could explain the results of many clinical empiricisms with our formula. We found that increasing Dcv and θ was more significant in reducing Eavf than increasing Dra and Da. Based on our model, we could define two critical energy loss rates (CELa, CELb) to help surgeons evaluate the blood vessels and choose the ideal range of θ, and help them design the preoperative RCAVF plan for each patient to increase the maturity and the primary patency of RCAVF.

The influence of joint geometric parameters on shape factor of butt joint with center through crack

In this research, the influence of such joint geometric parameters as weld width and reinforcement on shape ~actor of butt joint with center crack subjected to static loading was investigated by finite element analyses method. According to the analytical resuhs, a well fracture resistant joint shape of butt joint with center crack has been approved.

Research on the Change of Airfoil Geometric Parameters of Horizontal Axis Wind Turbine Blades Caused by Atmospheric Icing

Icing can significantly change the geometric parameters of wind turbine blades,which in turn,can reduce the aerodynamic characteristics of the airfoil.In-depth research is conducted in this study to identify the reasons for the decline of wind power equipment performance through the icing process.An accurate experimental test method is proposed in a natural environment that examines the growth and distribution of ice formation over the airfoil profile.The mathematical models of the airfoil chord length,camber,and thickness are established in order to investigate the variation of geometric airfoil parameters under different icing states.The results show that ice accumulation varies considerably along the blade span.By environmental temperature drop,the minimum and maximum extents of ice accumulation are observed near the blade root(0.2 R)and the blade tip(0.95 R),respectively(R represents the blade length).The icing process steadily increases the chord length and decreases the airfoil curvature,reaching the largest value at the blade tip region.Furthermore,the maximum curvature is reduced to 41.50%of the original curvature.The maximum camber position of the airfoil moves towards the trailing edge,and the most prominent position occurs at the middle blade region(0.6 R),where it moves back by 19.43%.Ice accumulation steadily increases airfoil thickness.It leads to the maximum thickness growth of 53.40%that occurs at the blade tip region and moves forward to the leading edge by 10%.The research results can provide the required theoretical support for further monitoring the blades operating conditions to ensure reliable wind turbines’operation.

Influence of Curve Geometric Parameters on Curving Performance of Sub-frame Radial Bogie

Based on the theory of vehicle-track coupling dynamics,the coupling dynamic model of the freight car mounted with the sub-frame bogies and the numerical model of curved track were established,utilizing the fast numerical integration method,the curving performance of the vehicle was simulated to study the influence of the curve geometric parameters such as curve radius,transition curve length and superelevation of outer rail on the wheel-rail dynamic interaction.The simulation results indicate that:(1)Increasing the curve radius can decrease the wheel-rail wear,but the effect will weaken while the curve radius is greater than 800m.(2)If the transition curve length is less than 30m,vibrations will appear at the transition-circle connecting point,and the smaller the transition length,the bigger the vibrations,the worse the wheel-rail wear,but when the length is bigger than 50m,its further variation has very little effect on wheel-rail wear.(3)The superelevation of outer rail can affect the distribution and difference of the inner and outer wheel-rail forces,and too large deficient or excessive superelevation will worsen the wheel-rail wear either.However,an appropriate deficient superelevation of outer rail(e.g.<20mm)is helpful to reduce the wheel-rail wear,which is consistent with the engineering practice of settling a certain deficient superelevation value.

On a Pair of Geometric Parameters of Orlicz Norm

For the geometric parameters Q and q of Orlicz norm, we prove where This result improves the traditional estimations of Chen S. T., Rao, M. M. and Wu C.X.

Geometric Calibration Method of Robot Based on Measurement System Including Position and Orientation Parameters

Industrial robot which can acquire high accuracy has been widely used in automatic assembly.Usually,the geometric parameter of industrial robot should be inspected during manufacturing and application.High precision measurement equipment was utilized to acquire the position and orientation of robot’s end⁃effector,when calibrating the geometric parameter of robot.A kind of measurement system based on a draw⁃wire encoder was presented,since the current measurement equipment has some disadvantages,such as the cost and the requirements of working environment are high.According to this kind of measurement system,a sort of geometric calibration method of robot was presented including position and orientation parameters.The uncertain arc length of the cable length between robot end⁃effector and the measurement can be exactly acquired according to the position and orientation parameters.The pose⁃solving model of robot end⁃effector was associated with the kinematic model of robot,and robot’s geometric parameter can be computed by using the least⁃squares methods.Validate instance was conducted,the result showed that the optimal number of the calibration pose was 47 with little improvement in accuracy,even if increasing the number of calibration pose.Robot calibration experiment was performed and the results showed that the absolute accuracy of robot decreased from 4.32 mm to 0.87 mm after calibration,which improved the robot’s absolute accuracy effectively.

Influences of Geometric Parameters upon Nozzle Performances in Scramjets

This article investigates and presents the influences of geometric parameters of a scramjet exerting upon its nozzle performances. These parameters include divergent angles, total lengths, height ratios, cowl lengths, and cowl angles. The flow field within the scramjet nozzle is simulated numerically by using the CFD software--FLUENT in association with coupled implicit solver and an RNG k-ε turbulence model.

Effects of critical geometric parameters on the optical performance of a conical cavity receiver

The optical performance of a receiver has a great influence on the efficiency and stability of a solar thermal power system.Most of the literature focuses on the optical performance of receivers with different geometric shapes,but less research is conducted on the effects of critical geometric parameters.In this paper,the commercial software TracePro was used to investigate the effects of some factors on a conical cavity receiver,such as the conical angle,the number of loops of the helical tube,and the distance between the focal point of the collector and the aperture.These factors affect the optical efficiency,the maximum heat flux density,and the light distribution in the conical cavity.The optical performance of the conical receiver was studied and analyzed using the Monte Carlo ray tracing method.To make a reliable simulation,the helical tube was attached to the inner wall of the cavity in the proposed model.The results showed that the amount of light rays reaching the helical tube increases with the increasing of the conical angle,while the optical efficiency decreases and the maximum heat flux density increases.The increase in the number of loops contributed to an increase in the optical efficiency and a uniform light distribution.The conical cavity receiver had an optimal optical performance when the focal point of the collector was near the aperture.

Geometric Parameters Corresponding to Representations of the Classical Groups with Integral Infinitesimal Characters

In this paper we calculate the orbits of flag manifolds of the complex classical groups under the action of the sets of fixed points of Cartan involutions, and determine all the geometric parameters corresponding to representations of the classical groups with integral infinitesimal char- acters, which are used to discuss Arthur conjecture and the Langlands classification of the irreducible admissible representations of real classical groups(see[1])

A new component maps correction method using variable geometric parameters

Accurate engine performance models are important for model-based performance evaluation of aero engine.The accuracy of the model often depends on engine component maps,so there is a need for a method that can accurately correct the component maps of the model over a wide range.In this paper,a new method for modifying component maps is proposed,this method combines the correction of the scaling factors with the solution process of the off-design working point,and uses the adjustment of the variable geometric parameters of the engine to change the position of the working line,in order to obtain more correction results and guarantee high accuracy in a wider range.The method is validated by taking the main fan of the Adaptive Cycle Engine(ACE),an ideal power unit for a new generation of multi-purpose and ultra-wide working range aircraft,as an example.The results show that the maximum error between the corrected component maps and the target maps is less than 1%.New possibility for more precise component maps can be realized in this paper.

Effect of geometric parameters at open turbine combined structure on flow field distribution of dry granulation for Si_(3)N_(4) powder

To improve the uniformity of the flow field and the poor axial velocity in the chamber of Si3N4 dry granulation, the influence of geometric parameters at open turbinecombined structure on the flow field distribution is studied. The Euler–Euler gas-solidtwo-phase flow model is established and the physical model of dry granulation chamberunder the combined structure is simplified. Under the same radial structure, the volumedistribution and velocity field of Si3N4 particles in the granulation chamber with a different number and angle of the axial structure at the open turbine are analyzed by theCFD method. The influence of the axial structure at the open turbine on the flow fielddistribution of Si3N4 particles under different geometric parameters is compared. Theresults show that the axial structure of the open turbine in the granulation chamber isthe most uniform when the number of blades is 6 and the inclination angle is 45◦, andthe circulating flow of the upper and lower parts of Si3N4 powder is strong.

PREDICTION OF PUMP CHARACTERISTICS ACCORDING TO GEOMETRICAL PARAMETERS OF IMPELLER AND VOLUTE CASING

The geometrical parameters of impeller or volute casing (including guide vane ofmultistage pump) have a great effect on pump characteristics, but ultimately. the pump characteris-tics are determined by the geometrical parameters of impeller and volute casing cooperatively. Inthis essay the effect of impeller and volute casing on pump characteristics will be studiedquantitatvely from the angle cf optimal matching of them.

透空结构与半潜式风机集成系统耦合运动响应特性分析

A novel semi-submersible platform is proposed for 5 MW wind turbines.This concept focuses on an integrated system formed by combining porous shells with a semi-submersible platform.A coupled aerodynamic–hydrodynamic–mooring analysis of the new system is performed.The motion responses of the novel platform system and the traditional platform are compared.The differences in hydrodynamic performance between the two platforms are also evaluated.The influence of the geometric parameters(porosity,diameter,and wall thickness)of porous shells on the motion response behavior of the new system is studied.Overall,the new semi-submersible platform exhibits superior stability in terms of pitch and heave degrees of freedom,demonstrating minimal effects on the motion response in the surge degree of freedom.

Analysis of the Hydraulic Performances of a New Liquid Emitter Based on a Leaf Vein Concept

The leaf-vein drip irrigation emitter is a new type of drip emitter based on a bionic structure able to support shunting,sharp turns,and increased dissipation.In the present work,the results of twenty-five tests executed in the framework of an orthogonal design strategy are presented in order to clarify the influence of the geometrical parameters of the flow channel on the hydraulic characteristics of such emitter.The corresponding flow index and head loss coefficient are determined through numerical simulations and model testing.The results show that the flow index of the flow channel is 0.4970∼0.5461,which corresponds to good hydraulic performances.The head loss coefficient of the flow channel is 572.74∼3933.05,which in turn indicates a good energy dissipation effect.The order of influence of the leaf vein flow channel parameters on the flow index can be represented in a synthetic way as a>b>c>d>e,where(a)is the width of the inlet,(b)is the horizontal distance of the front water inlet,(c)is the vertical distance of the inner edge of the front end,(d)is the horizontal distance of the rear water outlet and(e)is the vertical distance of the outer edge of the front end.The flow index increases with d,decreases with a,first decreases,and then increases with b,and first increases and then decreases with the increase of c and e.The coefficient(R^(2))of the fitted model related to geometric parameters and flow index is 0.9986-0.9999.The relative errors among experimental testing,simulation calculation and predictive estimates are shown to be less than 5%.

ELASTIC BEHAVIOR ANALYSIS OF 3D ANGLE-INTERLOCK WOVEN CERAMIC COMPOSITES

A micromechanical model for elastic behavior analysis of angle-interlock woven ceramic composites is proposed in this paper. This model takes into account the actual fabric structure by considering the fiber undulation and continuity in space, the cavities between adjacent yarns and the actual cross-section geometry of the yarn. Based on the laminate theory, the elastic properties of 3D angle-interlock woven ceramic composites are predicted. Different numbers of interlaced wefts have almost the same elastic moduli. The thickness of ceramic matrix has little effect on elastic moduli. When the undulation ratio increases longitudinal modulus decreases and the other Young＇s moduli increase. Good agreement between theoretical predictions and experimental results demonstrates the feasibility of the proposed model in analyzing the elastic properties of 3D angle-interlock woven ceramic composites. The results of this paper verify the fact that the method of analyzing polyester matrix composites is suitable for woven ceramic composites.

Natural Characteristic of Thin-Wall Pipe under Uniformly Distributed Pressure

Natural characteristics of thin?wall pipe of the compressor under uniformly distributed pressure were presented in this paper based on a cylindrical shell model. In the traditional method, the beam model was usually used to analyze the pipe system. In actual fact, the pipe segment of the compressor was always broken in the form of a long crack or a partial hole and the phenomenon was hardly explained by beam model. According to the structure characteristic of compressor pipe segment, whose radius is large and thickness is little, shell model shows the advantage in this kind of pipe problem. Based on Sanders’ shell theory, the vibration di erential equation of pipe was established by apply?ing the energy method. The influences of length to radius ratio(L/R), thickness to radius ratio(h/R), circumferential wave number(n) and pressure(q) on the natural frequencies of pipe were analyzed. The study shows: Pressure and structural parameters have a great e ect on the natural characteristics of the pipe. Natural frequency increases as the pressure increases, especially for the higher mode. The sensitivity of natural frequency on pressure becomes stronger with h/R ratio increases; when L/R ratio is greater than a certain critical value, the influence of the pressure on natural frequency will no longer be obvious. The value of n corresponding to the minimum natural frequency also depends on the value of pressure. In the end, analysis of the forced vibration of a specific pipeline model was given and the modal shapes were illustrated to understand the break of the pipe. The research here will provide the theory support for the dynamic design of related pressure pipe and further experiment study should be employed.

Research on the Design of a De-oiling Compound Hydrocyclone and Its Separation Characteristics

A compound hydrocyclone is a new strategy for oil-water separation. It is based on the study of static and dynamic hydrocyclones. In this paper are introduced its geometric traits and separation mechanism. Experiments are carried out about the relationship between geometric parameters ＆ operating parameters and the separation efficiency of the compound hydrocyclone. Under experimental conditions, the appropriate structural parameters optimized are as follows： The rotating grid is of the straight board type, 3 straight vanes with a length of above 95 ram; the diameter of the overflow vent ranges 3-12 ram; the separation efficiency is better when the large conical angle of the static vortex body is about 20° and the small conical angle in the range of 1° -4° ： The separation effect is better under the following conditions： The rotary speed is 1,700-2,400 r/min; the disposal capacity is 5.5 m^3/h; the loss of working pressure is 0.05-0.25MPa; and the split ratio ranges 5%-15%. The experimental study provides a certain basis for the design andapplication of the compound hydrocyclone.

Analysis of thermal conductivity in tree-like branched networks

Asymmetric tree-like branched networks are explored by geometric algorithms. Based on the network, an analysis of the thermal conductivity is presented. The relationship between effective thermal conductivity and geometric structures is obtained by using the thermal-electrical analogy technique. In all studied cases, a clear behaviour is observed, where angle （δ,θ） among parent branching extended lines, branches and parameter of the geometric structures have stronger effects on the effective thermal conductivity. When the angle δ is fixed, the optical diameter ratio β＋ is dependent on angle θ. Moreover, γand m are not related to β＊. The longer the branch is, the smaller the effective thermal conductivity will be. It is also found that when the angle θ〈δ2, the higher the iteration m is, the lower the thermal conductivity will be and it tends to zero, otherwise, it is bigger than zero. When the diameter ratio β1 〈 0.707 and angle δ is bigger, the optimal k of the perfect ratio increases with the increase of the angle δ; when β1 〉 0.707, the optimal k decreases. In addition, the effective thermal conductivity is always less than that of single channel material. The present results also show that the effective thermal conductivity of the asymmetric tree-like branched networks does not obey Murray＇s law.